The present invention relates in general to explosive warheads and in particular to a device for supporting the case during the pressing of the charge into a warhead.
For the pressed charges as used today, that is in particular hollow charges, the explosive charge is placed in the form of a precompact structure into the case together with the liner, and finish-pressed. To meet performance requirements, that is, in particular with a view to a high density and absence of fissures of the charge as well as to prevent a gap between charge and liner, during finish pressing a high pressure of generally more than 1000 bars is applied on the charge on the side of the liner.
The finish pressing of the charge is carried out either with or without a support mold, i.e. with a case whose circumference is exposed.
The supporting mold, which essentially surrounds the entire case, is pressed firmly against the case from the outside during the finish-pressing of the charge. It may consist, for example, of several shells, each with a wedge surface on the outside. During finish-pressing the shells with the hollow charge arranged therein are then inserted into an opening which is provided with corresponding wedge surfaces, so that by the joint action of their wedge surfaces with the wedge surfaces of the opening, the shells exert a high supporting pressure on the outside of the case.
Through the supporting mold however, an additional timeconsuming and expensive process step is introduced in the production of a hollow charge. Also the supporting mold is relatively expensive, and changes must be made in the pressing device.
The cases which are used for the finish-pressing of the charge without supporting mold are tested for pressure resistance beforehand, that is, before any parts such as charge etc. are inserted in them.
To this end an apparatus is used by which the cases are pressurized with water at a high pressure. Due to problems of sealing, the maximum attainable pressure is about 800 bars.
However, for the finish-pressing of the hollow charge without supporting mold at a pressing pressure of about 1500 bars and a holding time of 6 seconds, a deflagration with subsequent explosion has occurred, which has led to much damage to machines and buildings.
Various causes have been held responsible for this event. As the case was not smooth, that is, still showed tool marks, it was assumed, for example, that the deflagration was caused by the friction of the explosive along the case. Based on the appearance of case splinters which were found after the explosion, according to another assumption, too high a pressing pressure in the region of the ignition booster was held responsible.
Yet another assumption was that during the finish pressing, cracks developed in the case and that a crystal fracture of the explosive at the sharp edges of the cracks triggered the deflagration.
Several suggestions were made to counter the last-named cause. Thus, it was considered to reduce the finish-pressing pressure. This option, however, was dropped in view of the initiall mentioned performance requirements for pressed charges. Further, several testing methods for the case were proposed, e.g. by means of supersonics of holography techniques. But in view of the large quantities in the industrial production of pressed charges, these testing methods are unsuitable. Also increasing the strength of the case does give the desired result, because thereby its expansion is reduced, and reduced expansion may lead to easier bursting of the case. Also there has been a return to the above described supporting mold. If the fissuration in the case is the cause of said deflagration, this cause is not eliminated by the supporting mold, but is simply shifted into the firing device for the warhead. For then a deflagration does indeed not occur during finish pressing, because defective cases are no longer detected. But due to the high acceleration of the warhead, the case is exposed in the firing device to a pressure which is comparable to that during the pressure test, so that defects which only appear during pressing but do not become effective, will lead to fissuration and hence initiate the deflagration or explosion as the warhead is being fired.